In such a similar apparatus which is disclosed in U.S. Pat. No. 4,092,881 and corresponding German patent DE No. 2618877, the torque is provided exclusively by a pair of rotary drive cylinders which are disposed diametrically with respect to the main axis of the apparatus and can be actuated in the same direction to impart a limited rotary motion, in intermittent succession, to the rotatable chuck. Flexible pressure fluid lines lead from the source of fluid under pressure to the cylinders. Because the angle of rotation of the rotary motion of the rotatable chuck is predetermined and limited by the stroke of the rotary drive cylinders, the gripping engagement with the pipe member being turned must be released after each step of the rotary motion and be re-established again after the chuck has been turned back. This leads to an increased expenditure of time for carrying out the work of making or breaking a connection and many drilling tools comprise a plurality of connections. Another apparatus serving to make and break screw couplings or connections is also known and disclosed in German publication DE-AS No. 21 28 362, which uses a motor for the drive of the rotatable chuck, which motor engages with a pinion in a toothed rim mounted on the chuck. During the rotation of the rotatable chuck, the associated gripping apparatus remains connected to the pressure fluid source by a sealed rotary connection. Such rotary connections are expensive and susceptible to wear, require very narrow tolerances in size during manufacture and restrict the range of use of the apparatus to pipe members with small diameters. In addition, they can only be used for comparatively low working pressures because of the presence of moving seals and the tendency of the coaxial parts to be sealed with respect to one another to contract and expand when acted upon by pressure.
It is the object of the invention to provide apparatus for making and breaking screw couplings which ensures, with simple structural means, a rapid and reliable operation even when pipe members of large diameter are involved.